Contact-bank for automatic switching devices.



C. L. GOODRUM & H. F. DOBBIN.

CONTACT BANK FOR AUTOMATIC SWITCHING DEVICES.

APPLICATION FILED MAR. 23. 19I6.

1,227,90%D K Patent-ed May 29,1917.

//7 venfons Char/es L Goad/um y f. Dow/n.

UNITED STATES lPATlENT FFTGEQ CHARLES L. GOQDRUM AND HENRY F. DOBBIN', OF NEW YORK, N. Y., ASSIGNORS TO WESTERN ELECTRIC COMPANY, INCORPORATED; OF NEW YORK, N. Y., A CORPORA- TION OF NEW YORK.

Specification of Letters Patent.

Patented May 29, 1917..

Application filed March 23, 1916. Serial No. 86,173.

To all whom it may concern:

Be it known that we, CHARLES L. GoonRUM and HENRY F. DOBBIN, citizens of the United States, residing at New York, in the county of New York and State of New York, have invented certain new and useful Improvements in Contact-Banks for Automaticv Switching Devices, of which the followingis a full, clear, conclse, and exact description.

This invention relates to contact banks for automatic switching devices, and particularly to contact banks for switches of the panel type in which two movable contacts or brushes are employed.

The principal object of this invention is the provision of a contact bank composed of multiple pairs of contact strips so shaped and positioned that inductive action with the resulting crosstalk will be reduced to a minimum without the use of metallic strips or shield between the elements of each pair of terminal strips.

In contact banks in which the contact strips are formed of sheet material, it has formerly been necessary to interpose between the members of each pair of strips provided with the so called tip-and-ring contacts, a third strip provided with test or sleeve contacts which serves as a shield to prevent crosstalk. The present invention is intended to eliminate this third strip without lessening the efi'ectiveness of the device. This is accomplished by restricting the area of and offsetting the parts of the strips of the various pairs to practically eliminate the front elevation of a portion of a terminal illustrated in Figs. 2 and 3. However, the

inductive action. It is provided that the strips of the pairs be placed as nearly as possible in the same position with respect to the other adjacent strips of the bank in order that the currents induced in the two sides of the same pair may neutralize one another. It is' evident that if the two strips constitutin a pair or set are not in the same relative position with respect to the circuit from which the induced currents are received, the current in one strip of the pair will not be equal to the current in the other strip of the same pair, and hence there will be resulting crosstalk.

Referring to the drawings, Figure 1 is a bank; Fig. 2 is a sectional view taken on the line 2-'2 of Fig- 1; Fig. 3 is an enlarged a strip 4 of set perspective view of two sets, A and B of contact strips illustrating the preferred shape and arrangement of various strips of each of the sets.

1 indicates a portion of a switch bank of the preferred form built up of sets A and B of flat contact strips 2, 3, 4 and 5, separated by insulation and arranged in pairs. These strips have projecting contacts 12 and 13, and are apertured at 7 to receive the insulated bolts 8 and 9 by which the said strips are clamped in superposed position between the plates 10 and 11 in a manner similar to that described-in the patent to A. F. Dixon, No. 1,127,741.

Referring to Fig. 3, it will be noted that B has cut-out portions 4 -4 intermediate the alternate pairs of contacts. These cut-out portions equal substantially one-half the width of the strip and their lengths are substantially equal to the distance between the adjacent pairs of contacts. Shoulders 6 integral with the strips are located adjacent certain of the contacts. These shoulders are apertured at 7 to receive the insulated bolts 8 and 9 on which the strips are threaded as above stated. 'The companion strip 5 of this set is similarly constructed with cut-out portions 5 -5 ,but the parts are reversely arranged with respect to the strip 4. This arrangement of the cut-out portions provides in efiect a strip with alternately arranged ofi-set portions lying in the same plane as the strip, and when the strip is associated with its companion strip, produces in efiect lateral transpositions in the pairs of strips. Strip 2 of set A difiers from strip 4 of set B in thatthe former has ofi-set portions of a length twice as great as the OE- set portions in the strip 4. Strip 3 is similar number and position of the contacts can be changed-and other modifications can be readi ly substituted for the specific structure herein disclosed without departing from the spirit of this invention.

What is claimed is:

1. In a contact bank, flat terminal strips arranged in pairs, the strips of a pair having portions intermediate their ends offset in the plane of the strips to effect a transposed relationbetween portions of the strips.

2. In a contact bank, flat terminal strips arranged in pairs, the strips of a pair having alternately disposed portions projecting in the plane of said strips intermediate their ends, arranged to eifect a transposed relation between portions of the strips.

3. In a contact bank, pairs of flat terminal strips, portions in said strips oflset at right angles to the bank, the offset portions of each strip being reversely arranged with respect to its companion strip.

4:- In a contact bank, a pair of flat terminal strips, ofi-set portions in said strips, 's'aid ofiL-set portions being alternately disposed in flat strips arranged in pairs, the strips of one set having relatively long off-set portions reversely arranged, and the strips of the other set having relatively short reversely arranged oil-set portions.

6. In a contact bank, a pair of flat terminal strips, contacts projecting from each of said strips, said contacts being arranged in pairs, each member of the pair comprising a contact of eachof said strips, and a series of laterally disposed offset portions in each of said strips, the off-set portions of each strip being reversely arranged in the plane of said strip with respect to those of the other.

In Witness whereof, We hereunto subscribe our 'names'this 22nd day of March A. D.,

CHARLES L. GOODRUMQ HENRY F. DOBBIN. 

